score is easy to "game" as you well know. 
Fighter score only to some limit.
Of course fighter rank ain't a true 1-1 reflection of fighter skill. Not even close. But then, nothing is. We would have to define "fighting skills" first, which will run into problems... Asking for the "best pilot in the MA" is like asking for the "best plane" ... no definite answer on that
But to get into the top (let's say, 20), you need a very complete and significantly above average set of skills, ACM being just one (albeit important) of them. Mr. two weeker cant just decide to "game his way" to the top (At least not in LW - EW and MW is a different thing)
A good dueller is first and foremost good at one thing: Dueling, means applying ACM in a verly limited, clearly defined envronment. While many good duellers are also very good MA pilots (because they have additional skills at a high level as well), there a quite a few great duellers that fail in the chaotic and much greater context of the MA. You can be very good at basic 1v1 ACM, yet totally fail at developing battle awareness.
